1. Technical Field
The present invention relates to an image forming method, a process cartridge and an image forming apparatus.
2. Related Art
At present, a method of visualizing image information through an electrostatic image, such as electrophotography, is utilized in various fields. In the electrophotography, an electrostatic image (electrostatic latent image) is formed on a photoconductor (image forming member) by charge and exposure steps, and the electrostatic latent image is developed with a developer containing a toner and visualized through transfer and fixing steps. The developer which is used herein includes a two-component developer composed of a toner and a carrier and a single-component developer using a magnetic toner or a non-magnetic toner singly. As a method for manufacturing the toner, in general, a kneading pulverization manufacturing method in which a thermoplastic resin is melt kneaded together with a pigment, a charge controlling agent and a release agent such as waxes, and after cooling, the resulting mixture is finely pulverized and further classified is adopted. There may be the case where inorganic or organic particles for improving fluidity or cleaning properties are added onto the surface of the toner particle, if desired.
On the contrary, in an image forming method adopting the electrophotography, for the purpose of reducing the amount of energy consumption, technologies enabling one to perform fixing at a lower temperature are desired, and in particular, in recent years, in order to fully achieve energy conservation, it is desired to stop energization to a fixing device at the time of non-use. Accordingly, since the temperature of the fixing device is required to be raised to the use temperature in a moment at the time of energization, it is demanded to make the fixing temperature of the toner low.
As a measure for making the fixing temperature of a toner low, it is known to use a crystalline resin of a polycondensation type which reveals a sharp melt behavior against the temperature as a binder resin constituting the toner. However, a toner using a large amount of a crystalline resin is liable to cause yield deformation, and in the case where it is actually formulated into a toner, filming onto a conductor or a lowering with time of transfer efficiency due to toner collapse, etc. is easily caused.
As the foregoing related-art image forming method, since the acceleration of fixing by heating is a core rather than that by pressure, a reduction of energy at the time of fixing in an electrophotographic system does not significantly change the trend so that an improvement does not proceed, and in particular, there is no measure for realizing high-speed fixing by a simple fixing device, an aspect of which becomes important in correspondence to the printing market by the electrophotographic system. As a resin for toners capable of accelerating fixing by such heating, chain polymerization resins of a random monomer are widely used in all of addition polymerization and polycondensation.
On the contrary, in place of using thermal fixing, an image forming method using room-temperature pressure fixing by impressing a pressure of 20 MPa or more to a toner to subject the toner to plastic deformation and fixing it on paper is also used.
However, in this room-temperature pressure fixing system, since a high pressure of 20 MPa or more is used, the paper elongates, whereby the image becomes thick, or paper wrinkles are caused; and in the case where toner particles come into fibers of the paper, fixing failure in which fixing is not sufficiently achieved is easily caused. Therefore, an image forming apparatus using a pressure fixing system is not employed at the present, and a thermal fixing system is the main current.